Americans are celebrating the Labor Day holiday, a moment born as a salute to the nation's unionized workers that now has often morphed into a day of family gatherings marking the unofficial end of summer.

The first Monday in September became an official U.S. holiday in 1894 to celebrate a "workingman's holiday," and through the decades the country's industrialized centers often staged large parades honoring unionized factory workers.

But with the growth of technology and the globalization of the world economy, the U.S. labor movement has declined sharply. Many benefits sought by unions over the years, such as the basic five-day work week and employer-paid health care and vacations, have long been enshrined in much of the U.S. workplace.

Many U.S. corporations still actively oppose unionization of their workforces. Only about one-in-eight U.S. workers belongs to a union, about half the rate of 30 years ago. Many of union members work for local, state and federal governments in white-collar jobs, not in the gritty factories where the labor movement started.

The U.S. Labor Day is often celebrated as a day off from work with family picnics and outings, and in some communities it is the last day before children head back to classes for the start of a new school year on Tuesday.